Constructimn And Application Of Electrochemical Sensing Platform Based Onmetal-organic Framework Or Metal-hydroxide Composite Membrane

Hydrogen peroxide（H₂O₂）is the main product of human metabolism.As the main reactive oxygen species,high concentrations of hydrogen peroxide can damage human organs and the central nervous system,and even induce cancer.Uric acid（UA）is the final product of purine catabolism in the human body.Excessive uric acid in the human body may induce diseases such as gout,hyperuricemia,diabetes and high cholesterol.Effective detection of human metabolites H₂O₂ and UA is of great significance for prevention and disease diagnosis.At present,the electrochemical rapid and sensitive detection of H₂O₂ and UA still faces great challenges.In this paper,three modified electrodes based on organometallic framework nanocomposites or metal hydroxide composite films were constructed,and their electrochemical sensing properties for H₂O₂ or UA were studied,realizing highly sensitive electrochemical detection of H₂O₂ or UA.（1）The ZIF-8@ZIF-67 core-shell structure was prepared by the extensional growth method using imidazolic acid zeolite framework-8（ZIF-8）as the seed.Then,the gold nanoparticles（Au NPs）electrostatically adsorbed on the ZIFs core-shell structure were reduced by sodium borohydride,Au NPs/ZIF-8@ZIF-67 nanocomposites were prepared.The Au NPs in the composite enhanced the conductivity of the catalyst,and the core-shell structure of ZIFs provided a large specific surface area.The combination of the two inhibited the aggregation of Au NPs and ZIFs and improved the dispersion of each component.the modified glassy carbon electrode（GCE）with Au NPs/ZIF-8@ZIF-67reveals excellent electrocatalytic for the electrochemical reduction of H₂O₂.Under optimal conditions,the differential pulse voltammetry（DPV）was used to quantitatively detect H₂O₂,showing a good linear relationship in the range of 0.05～120μM,the detection limit was 0.016μM,and it had excellent anti-interference and stability.The sensor realizes the quantitative detection of H₂O₂ in hepatoma cells.（2）Ultrathin cobalt-aluminum layered double metal hydroxide nanosheets（Co Al-LDH_M/CC）were synthesized on carbon cloth（CC）by a one-step solvothermal method using dimethylimidazole（2-Me IM）as a complexing agent.The steady release of metal cations from the formed 2-Me IM-metal complex and hydroxide anions during the solvothermal process leads to the formation of ultrathin Co Al-LDH_M nanosheets on the surface of the CC substrate.The methanol solvent enhances the hydrophilicity of CC and increases the interlayer distance of LDHs nanosheets,making it better anchored on the surface of CC and increasing the mass transfer rate.The Co Al-LDH_M/CC electrode exhibited good electrocatalytic reduction performance for H₂O₂.Under the optimal conditions,the quantitative detection of H₂O₂ by i-t detection technology showed a good linear relationship in the range of 0.1μM～30 m M,and the detection limit was 0.030μM.After 14 days of storage at room temperature,the detected electrochemical signal remained at 94.5%of the initial level,showing good stability.（3）Au NPs/Ni Al-LDH composites were prepared by one-step synthesis of nickel-aluminum layered double metal hydroxide ultrathin nanosheets（Ni Al-LDH）,and then reduction of Au Cl₄^-electrostatically adsorbed on Ni Al-LDH nanosheets with sodium borohydride.The Au NPs/Ni Al-LDH composite maintains the sheet-like morphology of Ni AI-LDH,and its lateral scale increases and thickness decreases,indicating that more active sites are exposed.The composite of Au NPs improves the conductivity of the catalyst,so Au NPs/Ni Al-LDH exhibits good electrocatalytic oxidation activity for UA.Under optimal conditions,UA was quantitatively detected by DPV,and UA exhibited a good linear relationship in the range of 0.05～210μM,with a lower detection limit（0.010μM）.